Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270001
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
701 PM EST MON JAN 26 2015

.SYNOPSIS...
IN THE WAKE OF A STRONG DEPARTING LOW...DRY HIGH PRESSURE WILL
SPREAD BACK OVER THE REGION FROM THE NORTHWEST TONIGHT AND TOMORROW.
ANOTHER COLD FRONT IS EXPECTED TO CROSS THE REGION LATE THURSDAY
INTO EARLY FRIDAY WITH ANOTHER ROUND OF HIGH PRESSURE IN ITS WAKE.

&&

.NEAR TERM /THROUGH TUESDAY/...
645 PM UPDATE...SFC OBS FROM THE NW NC MTNS INDICATE SOME SNOW
SHOWERS ARE OCCURRING THERE...EVIDENTLY FROM BELOW RADAR BEAM LEVEL.
THE SMOKIES/BALSAMS HOWEVER APPEAR TO HAVE THE BEST CHANCE OF SEEING
NOTABLE ACCUMULATION...WITH THE PLUME OF MOISTURE FROM LAKE MICHIGAN
APPROACHING ALONG WITH THE CHANNELED VORT MAX. LIGHT RADAR
RETURNS ACCORDINGLY ARE SEEN OVER THE CUMBERLAND PLATEAU. SO IT
APPEARS THE SRN HALF OF THE MTN ZONES WILL BE THE FOCUS FOR PRECIP
IN THE EVENING...AND PERHAPS THE REST OF THE NIGHT WITH LATEST MODEL
PROGS SHOWING THE BEST SETUP FOR NW FLOW IN THE NORTH BEING RIGHT
NOW. WILL CONTINUE THE WSW AS-IS BUT PROVIDE UPDATED SNOW TOTALS
AND A REVISED TEXT PRODUCT BY 0300Z.

AS OF 245 PM EST MONDAY...BROAD FULL LATITUDE LONGWAVE UPPER TROF
REMAINS ACROSS THE EASTERN CONUS WITH SHARP RIDGING ACROSS THE WEST.
CLOSER TO HOME...BRISK NORTHWEST FLOW AMONGST THE AMPLIFIED UPPER
PATTERN AND POOLED LOW LEVEL MOISTURE CONTINUES TO YIELD LIGHT
UPSLOPE SNOW SHOWERS ALONG THE TN BORDER.  FURTHER EAST...FCST
FEATURES DECREASING POPS ACROSS NC PIEDMONT AS EARLIER SHOWER
ACTIVITY HAS DIMINISHED WITH ONLY A FEW LIGHT ECHOES EVIDENT ON
RADAR.  MODELS CONTINUE TO TREND TOWARDS A BRIEF LULL IN NORTHWEST
FLOW SNOW SHOWER ACTIVITY ALONG THE TN BORDER COUNTIES BEFORE A
SECOND ROUND OF CHANNELED VORTICITY SLIDES THROUGH THE REGION
TONIGHT.  LOW LEVEL MOISTURE ASSOCIATED WITH THIS ENERGY IMPULSE
WILL POOL ALONG THE MOUNTAINS ONCE AGAIN LEADING TO RE INITIATION OF
SNOW SHOWERS.  THUS...LIKELY/CATEGORICAL POPS ARE FEATURED IN THE
FCST.   MODEL QPF CONTINUES TO YIELD SUB WARNING CRITERIA SNOW
TOTALS THUS OPTED TO EXTENDED CURRENT ADVISORY THROUGH NOON TUESDAY
TO ALSO INCLUDE EXPANSION NORTHWARD INTO THE NORTHERN MOUNTAINS OF
WESTERN NC.  FORECAST ACCUMULATIONS WILL GENERALLY REMAIN AROUND 2
TO 3 INCHES WITH SOME 4 INCH TOTALS POSSIBLE ALONG THE HIGHER PEAKS
AND RIDGETOPS OF THE SMOKIES BY MORNING.  IN ADDITION TO THE
SNOWFALL...GUSTY NORTHWEST WINDS WILL PREVAIL THROUGH MUCH OF THE
NIGHT WITH SOME OF THE HIGHER ELEVATIONS SITES EXPERIENCING GUSTS
NEAR 40MPH...WHILE THE LOWER ELEVATIONS TOP OUT WITH GUSTS NEARING
25-30MPH.

OUTSIDE OF THE MOUNTAINS...CONDITIONS WILL GRADUALLY IMPROVE THROUGH
THE OVERNIGHT WITH SKIES BEGINNING TO SCT NEAR MIDDAY TUESDAY.
DOWNSLOPING FLOW WILL YIELD TEMPERATURES JUST BELOW NORMAL DESPITE
COLD ADVECTION PATTERN.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 230 PM MONDAY...THE FIRST PART OF THE SHORT RANGE LOOKS LIKE
THE QUIETEST PART OF THE ENTIRE FCST. ANY REMAINING NW FLOW SNOW
SHOWERS OVER THE NRN MOUNTAINS OF NC SHOULD TAPER OFF RIGHT AWAY
TUESDAY EVE. THE AXIS OF THE UPPER TROF SHOULD MOVE SLOWLY OFF THE E
COAST TUESDAY NIGHT...WHICH WILL KEEP A DRY NW FLOW OVERHEAD. AN
UPPER RIDGE WILL SLOWLY BUILD IN FROM THE WEST ON WEDNESDAY WITH THE
AXIS OF THE UPPER RIDGE MOVING OVERHEAD WEDNESDAY NIGHT. THIS WILL
SUPPORT DRY AND COOL HIGH PRESSURE THAT WILL KEEP TEMPS GENERALLY A
CATEGORY OR SO BELOW NORMAL.

ON THURSDAY...THE MODELS SHOW A PAIR OF SHORT WAVES MOVING THRU THE
MIDWEST AND AROUND A MEAN TROF OVER THE EAST. THE FIRST WAVE SHOULD
STAY OVER THE OH VALLEY ON THURSDAY AFTERNOON. WARM ADVECTION AHEAD
OF THE WAVE MAY HELP TO DEVELOP SOME LIGHT PRECIP ACROSS THE FCST
AREA...WITH THE BEST CHANCE OVER THE MTNS. FCST SOUNDINGS SUGGEST
THIS WILL BE AN ELEVATION-DEPENDENT RAIN OR SNOW SITUATION. THERE
SHOULD BE A SMALL CHANCE FOR PRECIP OUTSIDE THE MTNS THAT SHOULD
FALL AS RAIN. TEMPS WERE UNDERCUT FROM THE GUIDANCE...WITH THE
EXPECTATION THAT INCREASING CLOUDS AND SOME LIGHT PRECIP WILL
CONTINUE TO KEEP TEMPS BELOW NORMAL. THE SECOND WAVE SHOULD HELP TO
DRIVE A COLD FRONT ACROSS THE WESTERN CAROLINAS THURSDAY NIGHT. MOST
OF THE PRECIP WITH THIS FEATURE WILL BE CONFINED TO THE MTNS.
IMPROVING MOIST UPSLOPE FLOW BEHIND THE FRONT SHOULD MAINTAIN A
CHANCE OF PRECIP ON THE TN BORDER THROUGH AT LEAST DAYBREAK ON
FRIDAY. THIS SHOULD BE IN THE FORM OF SNOW SHOWERS OWING TO THE COLD
ADVECTION BEHIND THE FRONT. MIN TEMPS E OF THE MTNS SHOULD BE ABOVE
NORMAL BECAUSE OF LINGERING CLOUDS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 215 PM MONDAY...A PROMINENT TROUGH AXIS WILL MOVE QUICKLY EAST
OF THE FORECAST AREA FRI MORNING AND THEN OFF THE ERN SEABOARD
THROUGH THE DAY. SHALLOW MOISTURE IN THE NW FLOW COLD ADVECTION
BEHIND THE TROUGH COULD LINGER THROUGH LATE FRI MORNING...BUT WITH
LITTLE TO NO ADDITIONAL SNOW ACCUMULATIONS IN ANY UPSLOPE SHOWERS IN
THE WRN MTNS. MAXES WILL FALL BELOW CLIMO...PERHAPS 10 DEGREES OR
MORE BELOW CLIMO IN THE NC MOUNTAINS.

THE UPPER LEVEL FLOW PATTERN WILL BECOME ZONAL THROUGH SAT WITH SFC
HIGH PRESSURE LIKELY BUILDING OVER TO THE N OF THE REGION. A STEADY
INCREASE IN MID AND HIGH CLOUDS IS EXPECTED. MODEL DIFFERENCES THEN
APPEAR THROUGH THE LATTER HALF OF THE WEEKEND...WITH THE GFS
GENERALLY FASTER THAN RECENT ECMWF RUNS IN FEATURING A NRN STREAM
WAVE DIGGING INTO THE MIDWEST ON SUNDAY. THE 00Z OPERATIONAL ECMWF
WAS A BIT SLOWER...BUT THE 12Z RUN IS NOW CLOSER TO THE GFS TIMING
ON THE WAVE. THE MAIN SENSIBLE WEATHER DIFFERENCE FOR SUNDAY IS THAT
THE FASTER GFS TIMING ALLOWS PRECIPITATION TO ARRIVE BY
DAYBREAK...WITH A SRN TIER FREEZING RAIN/NRN TIER SNOW AND SLEET
THREAT...WITH RELATIVELY PROMINENT CAD SETTING UP FROM THE NE.
PROFILES WOULD THEN WARM FOR THE PEAK OF THE WARM ADVECTION...WITH
MAINLY A RAIN PTYPE EXCEPT FOR LINGERING FZRA IN ANY COLD POCKETS
JUST E OF THE BLUE RIDGE. THE ECMWF HAS A SLOWER ONSET OF
PRECIPITATION...WITH LESS MORNING FREEZING RAIN THREAT...MUCH WEAKER
CAD...BUT THEN MORE OF A RAIN VERSUS SNOW PTYPE ISSUE THROUGHOUT THE
WHOLE EVENT. SUNDAY TEMPS HAVE BEEN LOWERED SLIGHTLY...AND PTYPES
REMAIN RAIN/SNOW.

DIFFERENCES ARE MORE STARK SUN NIGHT INTO MONDAY. THE GFS DRIVES A
COLD FRONT THROUGH THE REGION AND DRIES THINGS OUT...OTHER THAN ANY
LINGERING NW FLOW MOISTURE IN THE WRN MTNS. THE ECMWF...ON THE OTHER
HAND...DEVELOPS A SFC WAVE OVER THE SE AND KEEPS HEAVY PRECIPITATION
IN THE REGION SUNDAY NIGHT INTO MONDAY. ASSOCIATED PTYPE ISSUES
WOULD CONTINUE DEPENDING ON THE SFC LOW TRACK. WILL CONTINUE TO KEEP
ALL PTYPES RAIN VERSUS SNOW THROUGHOUT GIVEN ALL THE UNCERTAINTY IN
THERMAL PROFILES.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AT KCLT...VFR BUT WITH A CIG PERSISTING MOST OF THE EVENING. BASES
WILL GRADUALLY LIFT AND SCATTER...BUT A POCKET OF MIDLEVEL MOISTURE
WILL PASS OVERHEAD LATE TONIGHT BRINGING CIGS BACK FOR A TIME
LASTING THRU THE MRNG. NWLY WINDS ARE LIKELY TO GUST AT LEAST
OCCASIONALLY THIS EVENING IN COLD ADVECTION AND TIGHT PRESSURE
GRADIENT. MIXING WILL DIMINISH AFTER MIDNIGHT WHICH SHOULD ALLOW
WINDS TO WEAKEN. A FEW GUSTS ARE LIKELY TO RETURN TUE BUT A FAIRLY
STEADY NW BREEZE WILL PREVAIL.

ELSEWHERE...VFR EAST OF THE MTNS...WHERE MOIST NW FLOW WILL CONTINUE
THRU TONIGHT AND TUE MRNG BENEATH A PERSISTENT UPPER TROUGH OVER
THE EAST COAST. A CHANNELED STREAM OF VORTICITY MAY PROVIDE SOME
ENHANCEMENT TO FORCING BUT SNOWFALL RATES WILL MAINLY BE DETERMINED
BY WIND SPEED AND LLVL MOISTURE. KAVL WILL CONTINUE TO SEE MVFR TO
LOW VFR CLOUDS THRU MORNING THOUGH ANY PRECIP WILL REMAIN NEARER THE
TENN BORDER. NWLY GUSTS WILL AFFECT ALL THE SITES THIS EVENING
BEFORE DIMINISHING WITH THE PRESSURE GRADIENT LATER TONIGHT...BUT
THEY WILL PICK BACK UP WITH MIXING BY LATE MRNG.

OUTLOOK...A SERIES OF CLIPPER SYSTEMS WILL BRING PERIODIC CHANCES
FOR SNOW SHOWERS...MAINLY TO THE MOUNTAINS THROUGH THE WEEK. MOST OF
THESE SNOW SHOWERS WILL REMAIN WEST AND NORTH OF KAVL...BUT BRIEF
PERIODS OF RESTRICTIONS AND SNOW SHOWERS CANNOT BE RULED OUT THERE.
OTHERWISE...MAINLY VFR CONDITIONS ARE EXPECTED.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   56%     LOW   56%     MED   67%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TUESDAY FOR NCZ033-
     048>052-058-059.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...CDG/WIMBERLEY
SHORT TERM...PM
LONG TERM...HG
AVIATION...WIMBERLEY


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